Method of removing enamel from electrical conductors



I Patented 27,- 1927.

UNITED STATES 1,653,805 PATENT OFFICE.

WILLIAM G. HOUSKEEPER, OF SOU'IH ORANGE, NEW JERSEY, ASSIGNOR T WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

METHOD OF REMOVING ENAMEL FROM ELECTRICAL CONDUCTORS.

No Drawing.

This invention relates to electrical conductors.

An object of. the invention is to facilitate the soldering of insulatedconductors.

A related object of the invention is to provide an efiicient andinexpensive method of removing enamel or similar insulation fromelectrical conductors. x

The invention is particularly applicable to telephone switchboard cableand distributing frame wire, which are used extensively in telephoneexchanges.

Conductors of this type commonly consist of tinned copper wire,insulated with a layer of black enamel, and provided with one, two, oreven three wrappings of'fibrous material, such as cotton or floss silk,to secure a high insulation resistance. A suitable enamel which has beenemployed for insulating conductors of this type and a' method of apply-.ing the enamel to the bare .conductor, are disclosed and claimed inPatent No. 1,101,281 to H. B. Holmes and J. WV. Harris, issued June 23,1914. The process of making the the treatment of insulating coating orenamel described there in generally consists in dissolving a solidhydrocarbon and castor oil solvent, applying the solution to an articleto be'coated and then subjecting the coating to a temperature 30approximating 260 to 270 C. Before soldering such insulated conductorsto the terminals of apparatus in a tele-' phone exchange, it iscustomary to dip the conductors in a beeswax compound bath of about 50%beeswax with 50% paraflin by weight to thoroughly impregnate thefibrous. insulation adjacent the exposed ends in order to prevent theingress of moisture and to prevent fraying of the in- 40 sulation. Aportion of the fibrous insulation is then removed from the conductor,usually by employing a pair of long-nose pliers to crush the insulationat the desired point and in the same'operation stripping or skinning theinsulation from'the conductor. Ordinarily, the hard layer of enamel isnot affected by the stripping operation, although in rare cases aportion offthe enamel may come off with the fibrous insulation.

When the desired length of fibrous insulation has been stripped from theconductor without removing the enamel, it is then necessary to removethe enamel before or dur- Application filed February 10, 1926. SerialNo. 87,461.

ing the soldering operation. Heretofore, attempts have been made toremove the enamel by mechanically scraping it from the wire, or else bymeans of a hot soldering iron or by using a special enamel removing fluxwithin the core solder. When either of the last two methods is used,however, a portion of the enamel may remain in the joint and, beingcovered with solder,result ina defective contact, difiicult to locateby. visual inspection. Moreover, enamel softenin fluxes frequently giveolf' poisonous and ot er 0bnoxious gases which are a serious healthhazard.

The difficulties outlined above are overcome by this invention whichconsists, briefly, in the application to the wire before soldering of amaterial or materials which will serve to spften the enamel suflicientlyso that, after the usual beeswax compound treatment, the enamel isremoved with the fibrous insulation at the time of stripping, thuspresenting a clean surface free of enamel which may be soldered byordinary methods.

The preferred method of carrying out the invention consists in immersingthe conductor or conductors for about five minutes in monochlor-henzolat room temperature. The

conductor or conductors so treated may then be dipped in the beeswaxcompound, until the fibrous insulation is thoroughly impregnated, andare then stripped in the manner described above, with the result thatthe enamel is readily removed with the fibrous insulation.

.Other enamel softening solutions which may be used successfully aresaturated solutions of salicylic acid in monochlor-benzol and of benzoicacid in alcohol. Stearic acid, rosin, and rosin oil may be used in somecases, but each of these materials requires heating to a temperaturewhich may result in injury to certain kinds of fibrous insulation.

An important advantage is obtained by removing the enamel before thesoldering operation inasmuch as it precludes the possibility of enamelbeing present in the joint, which usually occurs when an enamel removingflux is used at the time of soldering.

It is to be understood that the invention is also capable of othermodifications and adaptations not specifically referred to but includedwithin the scope of the appended claim.

What is claimed is: The method of treating an electrical con- 5 ductorinsulated witha layer of enamel-like material comprising a solidhydrocarbon and a non-drying vegetable oil subjected to destructivedistillation and a wrapping of fibrous material, which comprises,treating 10 the conductor with monoehlor-benzol for 21.

period of time suflicient to soften the enamel, immediately thereafterimpregnating the fibrous insulation with wax, and stripping the fibrousinsulation and enamel from the conductor.

In witness whereof, I hereunto subscribe my name this 8th day ofFebruary, A. D., 1926.

WILLIAM G. HOUSKEEPER.

